Piezoelectric ceramics

ABSTRACT

PIEZOELECTRIC CERAMICS ARE PROVIDED CONSISTING ESSENTIALLY OF A SOLID SOULTION OF PB(LI1/4SB3/4)O3, TBTIO3 AND PBZRO3 WHERE UP TO 25 ATOM PERCENT OF PB MAY BE REPLACED BY AT LEAST ONE OF BA, SR AND CA, AND MANGANESE OXIDE IN THE AMOUNT OF 0.10 TO 3.0 WEIGHT PERCENT IN THE FORM OF MNO.

Dec. 28, 1971 TQMEJ] QHNO ETAL 3,630,907

PIEZOELECTRIG CERAMICS Filed July l0, 1969 2 Sheets-Sheet l INVENTORS TOMEJI OHNO MASAO TAKAHASHI TSUNEO AKASHI NORIO TSUBOUCHI B Y /M, @ff/@KTM Dec. 28, 1971 TOMEJl OHNO ETAL 3,630,907

' PIEzoELEcTRIc CERAMICS Filed July 10, 1969 2 sheets-sheet 2 FIG. 2

/NvE/vrons TOMEJI OHNO MASAO TAKAHASHI TSUNEO AKASHI NORIO TSUBOUCHI United States Patent O "i 3,630,907 PIEZOELECTRIC CERAMICS Tomeji Ohno, Masao Takahashi, Tsuneo Akashi, and Norio Tsubouchi, Tokyo, Japan, assignors to Nippon Electric Company, Limited, Minato-ku, Tokyo, Japan Continuation-impart of application Ser. No. 681,494, Nov. 8, 1967. This application .Iuly 10, 1969, Ser. No. 840,788 Claims priority, application Japan, July 12, 1968, 43/ 49,407 The portion of the term of the patent subsequent to July 27, 1988, has been dsclaimed Int. Cl. C04b 35/46, 35/48 U.S. Cl. 252-629 3 Claims ABSTRACT OF THE DISCLOSURE Piezoelectric ceramics are provided consisting essentially of a solid solution of Pb(Li1/4Sb3/4)G3, PbTiO3 and PbZrO3 where up to 25 atom percent of Pb may be replaced by at least one of Ba, Sr and Ca, and manganese oxide in the amount of 0.10 to 3.0 weight percent in the form of MnO.

This application is a continuation-in-part of U.S. application Ser. No. 681,494, filed Nov. 8, 1967, now Pat. No. 3,595,795.

This invention relates to piezoelectric materials and more particularly to piezoelectric ceramics having eX- cellent piezoelectric properties.

BACKGROUND OF THE INVENTION The fundamental measures for evaluating the piezoelectric properties of a piezoelectric material are the electromechanical coupling factor and the mechanical quality factor. The former is a representative of the efficiency of transforming electrical oscillation into mechanical vibration and of conversely transforming mechanical vibration into electrical oscillation. A greater elecromechanical coupling facor indicates for better eiciency of interconversion. The latter factor shows the reciprocal proportion of the energy consumed by the material during the energy conversion, larger mechanical quality factor indicating for smaller energy consumption.

One of the typical fields of application for piezoelectric materials is in the manufacture of elements for ceramic filters. In this case, it is desirable to provide an electromechanical coupling factor with an optimum Value selected from a wide range between the extremely great and the very small while the mechanical quality factor should assume as large a value as possible. This fact is fully described in, for example, R. C. V. Macario, Design Data for Band-lPass Ladder Filter Employing Ceramic Resonators which appears in Electronic Engineering, Vol. f

33, No. 3, (1961) pp. 171-177.

The transducer elements of mechanical iilters provide another important iield of application of piezoelectric ceramics. In this case, both the electromechanical coupling factor and the mechanical quality factor should be as large as possible.

In a copending application U.S. Ser. No. 681,494 of which this application is a continuation-impart tiled by the same applicant, there is disclosed novel piezoelectric ceramics of Pb(Li1/4Sb3/4)Oa-PbTiOg-PbZrO3. Although these ceramics have a remarkably large electromechan- 3,630,907 Patented Dec. 28, 1971 Ice ical coupling factor, the mechanical quality factor is low and hence the fields of application are rather restricted. They are not suited for use in the manufacture of elements for ceramic filters and transducer elements for mechanical filters.

OBJECTS OF THE INVENTION The object of this invention is to provide piezoelectric ceramics haaing high values for both the electromechanical coupling factor and the mechanical quality factor.

Another object of this invention is to provide piezoelectric ceramics suited for use in elds such as the manufacture of elements for ceramic filters and the transducer elements of mechanical filters.

SUMMARY OF THE INVENTION This invention is characterized by 4the ceramic compositions consisting essentially of a solid solution of Pb(Lil/,Sbs/.QO3-PbTiO3-PbZrO3 ternary system and manganese oxide ranging from 0.10 to 3.0 Weight percent. The lead (Pb) contained in the basic Pb(Li1/4Sb3/4)O3 PbZrO3 composition may be replaced, up to 25 atom percent thereof, by barium (Ba), strontium (Sr) or calcium (Ca).

Where the basic Pb (Lil/Sbm)O3-PbTiO3-lbZrO3 composition is represented by the compositional formula [Pb(Li1/4Sb314)O3]x[PbTiO]y[PbZdO3]z where x, y, and z are a set of mol ratios and x-|-y-l-z=l.00, the composition should be restricted within the range determined by the following combinations of the mol ratios x, y and z:

x y z Incorporation of manganese oxide (MnO) in the amount of `0.10 to 3.0 weight percent into the basic composition mentioned above improves the mechanical quality factor without fatal decrease inthe electromechanical coupling factor and produces useful piezoelectric ceramics applicable to the elements of ceramic filters and the transducer elements of mechanical filters.

BRIEF DESCRIPTION OF THE DRAWINGS The excellent piezoelectric properties of the ceramic compositions of this invention will be apparent from the following description of preferred examples as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a composition diagram of the ternary system showing both the effective ranges of the basic compositions of the ceramics of this invention and particular basic compositions; and

FIG. 2 illustrates graphically the lelectromechanical coupling factor and the mechanical quality factor of the ceramics of this invention, as a function of the amount of manganese oxide in the compositori.

DETAILED DESCRIPTION Powdered materials of lead monoxide (PbO), lithium carbonate (Li2CO3), antimony sesquioxide (SbzOa), titanium dioxide (TiOz), zironium dioxide (ZrO2) and manganses carbonate (MnCO3) are used as starting materials to obtain the Pb(Li1/4Sb3/4)O31PbTiO3PbZrO3 ceramics containing manganese monoxide. These powdered materials are so proportioned that the final composition may comprise various mol ratios x, y, and z of the basic composition with the manganese monoxide varying in amount from 0.00 to 3.0 weight percent as shown in Table 1. Furthermore, barium carbonate (BaCO), strontium carbonate (SrCO3) or calcium carbonate (CaCO3) may be added to above starting materials to obtain the ceramics having compositions shown in Table 2, in which u atom percent of lead (Pb) of the basic composition having the mol ratios x, y and z of the Pb(Li1/4-Sb3/4)O3, PbTiO3 and PbZrO3 components is replaced by barium (Ba), strontium (Sr) or calcium (Ca) represented by Me in the table. Lithium carbonate (Li2CO3), antimony sesquioxide ($13203), manganese carbonate (MnCOg), and barium, strontium or calcium carbonate (BaCO3, SrCO3 or CaCO3) are proportioned as calculated on the basis of lithium oxide (Li3O) antimony pentoxide (Sb205), manganese monoxide (MnO), antimony pentoxide (Sb205), manganese monoxide (MnO), and barium, strontium or calcium oxide (BaO, SrO or CaO), respectively.

The respective powders are mixed in a ball mill with to filtration, dried, crushed, then presintered at 900 C. for one hour, and again crushed. Thereafter, the mixtures, with a small amount of distilled water being added thereto, are press-molded into discs of mm. in diameter at a pressure of 700 kg./cm.2 and sintered in an atmosphere of lead monoxide (PbO) for one hour at a temperature of 1260 to 1300 C. The resulting ceramic discs are polished to a thickness of one millimeter, provided with silver electrodes on both surfaces, and thereafter piezoelectrically activated through polarization treatment for one hour at 100 C. under an applied D C. electric field of 30 to 50 lim/cm.

After the ceramic discs stand for 24 hours, the electromechanical coupling factor for the radial mode vibration k, and the mechanical quality factor Q.m may be measured to evaluate the piezoelectric properties. Measurement of these piezoelectric properties may be made in accordance with the IRE standard circuit. The value of kr is calculated by the resonant to antiresonant frequency method. The dielectric constant e and the dielectric loss (tan are also measured at a frequency of l kHz.

Tables 1 and 2 show typical results obtained. The basic compositions of the specimens of Table 1 are shown in the ethyl alcohol. The mixed powders are then subjected 25 FIG. 1 by the points located inside the triangle.

TABLE 1 Mol ratio of basic composition Additive agent,

Pb(Li1/4 MnO Sbs/003, PbTiOa, PbZrOa, (wt. k.- Tan z y z percent) (percent) Qm e (percent) 0.30 0. 23 0. 47 0. 00 11 320 570 26 0. 0. 23 0. 47 0.10 12 700 460 1. 9 0. 30 0. 23 0.47 0.20 13 950 490 1. 2 0. 30 0.23 0. 47 0.50 13 2, 240 550 1. 3 0.30 0. 23 0. 47 1.0 10 2,260 920 1.4 0.30 0. 23 0.47 2.0 8 1, 140 650 2. 0 0. 30 0. 23 0.47 3. 0 7 600 530 2. 5 0. 20 0. 33 0. 47 0. 00 26 170 830 2. 9 0.20 0.33 0. 47 0.10 24 350 760 1. 5 0. 20 0. 33 0. 47 0.20 24 740 680 1. 3 0.20 0.33 0. 47 0. 50 23 2, 770 680 1. 2 0. 20 0.33 0.47 1.0 22 2, 400 760 1. 5 0.20 0.48 0.32 0.00 25 180 630 1. 9 0.20 0. 48 0.32 0. 10 17 390 560 1.6 0. 20 0.48 0.32 0.20 16 960 470 1. 4 0. 20 0.48 0. 32 0.50 22 2, 250 570 1. 2 0. 20 0.48 0. 32 1.0 31 1I 640 800 1. 5 0. 20 0. 48 0.32 2.0 37 900 1, 240 1.8 0.20 0. 48 0. 32 3. 0 31 390 1, 130 2.0 0. 10 0. 40 0. 50 0.00 53 110 870 2. 3 0. 10 0. 40 0. 50 0. 10 51 280 780 1. 5 0. 10 0. 40 0. 50 0. 20 52 770 700 1. 0 0.10 0. 0.50 0. 50 46 2, 650 590 1. 1 0.10 0.40 0.50 1. 0 44 2, 610 510 1. 1 0.10 0.48 (l. 42 0. 00 54 120 1, 640 1. 3 0.10 0.48 0.42 0.10 52 310 1, 470 1. 2 0.10 0.48 0. 42 0. 20 49 390 1, 390 1.0 0. 10 0. 48 0.42 0.50 61 950 1, 420 1. 2 0. 10 0. 48 0.42 1.0 64 890 1, 470 1. 3 0.10 0. 48 0.42 2. 0 32 530 1, 260 1. 5 0. 10 0. 48 0. 42 3. 0 26 400 1, 180 1. 8 0. 05 0.20 0.75 0.00 28 270 450 2. 4 0.05 0. 20 0.75 0.10 25 630 380 1. 9 0.05 0.20 0.75 0. 20 24 2, 610 460 1. 1 0.05 0.20 0.75 0.50 22 1, 970 410 1. 2 0.05 0.43 0.52 0.00 61 95 790 2. 1 0.05 0.43 0.52 0.10 56 280 680 1. 5 0. 05 0. 43 0.52 0. 20 58 890 570 1.0 0.05 0.43 0.52 0.50 49 2, 060 400 1. 0 0.05 0. 43 0.52 1. 0 41 1, 510 430 1. 2 0. 05 0. 43 0.52 2. 0 30 720 380 1. 5 0. 05 0. 43 0. 52 3. 0 24 510 350 2.2 0. 05 0. 46 0.49 0. 00 71 87 965 3. 1 0.05 0. 46 0. 49 0. 10 63 240 1, 020 1. 2 0. 05 0.46 0.49 0.20 67 1y 250 705 0. 9 0. 05 0. 46 0. 49 0. 30 62 1, 600 640 0. 8 0. 05 0. 46 0.49 0.50 56 1, 890 450 0.8 0.05 0.55 0.40 0.00 43 130 810 1. 2 0.05 0. 0.40 0.10 32 560 700 1. 1 0.05 0.55 0.40 0. 20 35 620 650 0. 9 0.05 0. 55 0.40 0.50 25 3,190 540 0.9 0. O2 0. 47 0.51 0. 00 80 80 1, 190 1. 4 0.02 0. 47 0. El 0. l0 49 480 880 1. 3 0. 02 0. 47 0. 5l 0. 20 52 890 610 1. 2 0.02 0. 47 0. 51 0. 50 63 1, 260 E80 1. 0 0.02 0.47 0. 51 1. 0 51 800 560 1. 4 0. 01 0. 70 0. 29 0. 00 6 210 370 2. 4 0.01 0. 0. 29 0. 10 7 630 410 1.0 0.01 0. 70 0. 29 0. 60 8 1, 680 360 1. 0 0. 01 0. 70 O. 29 3. 0 6 480 340 2. 2 0. 01 0. 09 0. 90 0. 00 16 470 270 4. 4 0.01 0.09 0.90 0. 10 14 700 250 1. 2 0.01 0. 09 0. 90 0. 50 13 1, 880 210 1. 0 0. 01 0. 09 0.90 3. 0 10 630 200 3. 5 0. 05 0. 05 0. 90 0. 00 9 530 370 2. 2 0.05 0. 05 0. 90 0. 10 8 780 350 1. 0

TABLE l-Continucd Mol ratio of basic composition Additive agent, Pb(Li1/4 MnO Sbs/4) Os, PbTiOa. PbZrOa, (wt. lrr Tan a: z percent) (percent) Qm e (percent) 0. 05 0. 05 0. 90 0. 50 7 1, 790 320 1. 1 0. 05 0. 05 0. 90 3. 0 6 650 300 2. l 0. 30 0. 05 0. 65 0. 00 8 110 450 5. 6 0. 30 0. 05 0. 65 O. 10 8 480 410 2. 0 0. 30 0. 05 0. 65 0. 50 6 1, 710 380 1. 4 0. 30 0. 05 0. 65 3. 0 5 790 360 3. 3 0. 30 0. 50 0. 20 0. 00 10 280 170 3. 5 0. 30 0. 50 0. 20 0. 10 l2 670 160 2. 0. 30 0. 50 0. 20 0. 50 12 1, 760 140 1. 5 0. 30 0. 50 0. 20 3. 0 10 800 140 3. 3 0. l 0. 70 0. 20 0. 00 10 410 320 2. 8 0. 10 0. 70 0. 20 0. 10 11 930 280 1. 3 0. 10 0. 70 0. 20 0. 50 10 2, 010 260 1. 1 0. 10 0. 70 0. 20 3. 0 8 670 250 2. 5

Norm-The specimens Whose numbers have a solo asterisk are not included within the scope of this invention; in manufacture of the specimens with double asterisks, manganese dioxide (MnOz) is used instead of manganese carbonate (MnCOa) as one oi the starting materials.

TABLE 2 Basic Composition MnO, Weight Number :c y 2 u Me percent l- Qm e tan 1 0.02 0. 45 O. 53 0.05 Ca 0.00 74 90 2, 280 2. 6 0.02 0.45 0.53 0. Ca 0. 10 56 430 1, 580 1. 5 0. 02 0. 45 0.53 0.05 Ca 0.50 63 1, 420 1, 250 1.6 0. 02 0. 45 0.53 0.05 Ca 3. (l 40 590 930 2. 4 0. 02 0. 42 0. 56 0. 10 Ca 0. 00 68 75 3, 020 2. 7 0.02 0. 42 0. 56 0.10 Ca 0.10 51 390 2,660 1. 3 0.02 0.42 0.56 0.10 Ca 0.50 62 1, 310 2, 310 1.5 0.02 0. 42 0.56 0.10 Ca. 3. 0 35 480 2, 050 2. 5 0.02 0.47 0.51 0.02 Sr 0. 00 69 90 1, 820 2. 5 O. 02 0.47 0.51 0.02 Sr 0.10 41 500 1, 210 l. 3 0.02 0.47 0. 51 0.02 Sr 0.50 56 1, 450 1, 060 1. 7 0.02 0.47 0.51 0.02 Sr 3.0 33 180 680 2. 3 0. 05 0.43 0. 52 O. 10 Sr 0.00 74 90 2, 580 3. l 0.05 0.43 0.52 0.10 Sr 0.10 55 460 2, 200 1. 8 0.05 0.48 0.62 0.10 Sr 0.50 60 1, 830 1, 860 1. 5 0.05 0.43 0.52 0.10 Sr 3.0 35 470 1, 590 2. 9 0.02 0.48 0.50 0.05 Ba 0. 00 73 90 1, 760 2. 3 0.02 0.48 0.50 0.05 Ba 0.10 51 470 1, 160 1.1 0.02 0.48 0.50 0. 05 Ba 0. 50 62 1, 940 780 1. 3 0. 02 0.48 0.50 0.05 Ba 3.0 40 390 510 2.0 0. O5 0. 46 0.49 0.10 Ba 0.00 66 80 2, 240 2. 8 0.05 0.46 0.49 0.10 Ba 0.10 39 520 1, 580 1. 5 0.05 0.46 0.49 0.10 Ba 0.50 53 1, 930 1, 210 1. 7 0.05 0.46 0.49 0.1() Ba 3.0 31 610 930 2. 5

Moreover, it has been found that the superior piezoelectric properties as shown and mentioned are available when the basic compositions represented by the formula x y z If the basic compositions do not fall within the abovementioned area, the resultant ceramics possess rather inferior piezoelectric properties of little use.

Table 2 reveals that excellent piezoelectric properties are possessed by the ceramics in which a part of the Pb of the basic composition is replaced by Ba, Sr, or Ca. In general, at least one or Ca may replace up to atom percent of Pb contained in the basic composition.

It should be noted that the improvement made in the piezoelectric properties by incorporation of MnO clearly results from the presence of manganese ions. There are various known methods for producing manganese ions by using as a starting material manganese oxide itself (such as MnO or Mn02) or some other manganese compound such as MnCO3. The latter is easily decomposed at elevated'temperature to form manganese oxide. If a manganese compound other than MnO is utilized, it should be used in an equivalent amount as calculated on the basis of MnO. In the above examples, M11CO3 is mostly used instead of MnO. The -use of Mn02 is exempliiied in NOS. l0, 38, 46, and 54 of Table l.

It will be apparent that the starting materials to be used in the manufacture of the ceramics of this invention are not limited to those used in the above examples. It may be observed that those oxides which are easily decomposed at elevated temperature to form the required compositions may be used instead of the starting materials of the above examples, for example Pb304 may be substituted for PbO. Also, those salts such as oxalates or carbonates may be used instead of the oxides used in the examples, which such salts being easily decomposed into the respective oxides at elevated temperatures. Otherwise, hydroxides of the same character as above, may be used instead of the oxides. Moreover, an excellent piezoelectric ceramic material having similar properties to the above examples is obtainable by preparing in advance separately the powdered material of each of and of any starting material for MnO in advance and by using them as starting materials to be mixed subsequently.

It is usual for zirconium dioxide (Zr02) available in the market to contain several percent of hafnium dioxide (HtOg). Accordingly, the ceramic compositions of this invention may contain small amounts of oxides or elements existing in materials available in the market.

While there has been described what at present is believed to be the preferred examples of this invention, it will be obvious that various modifications can be made therein Without departing from the scope of this invention and lthat this invention covers all the ceramic compositions as specified in the appended claims.

7 What we claim is: 2. The piezoelectric ceramics claimed in claim 1, in l. Piezoelectric ceramics consisting essentially of a which up to 25 atom percent of Pb in said solid solution solid solution of Pb(Li1/4Sb3/4)O3, PbTiO3 and PbZrO3 is replaced by at least one of Ba, Sr and Ca. and manganese oxide in the amount of 0.10 to 3.0 weight 3. The piezoelectric ceramics claimed in claim 1, in percent calculated as MnO, the composition of said Solid 5 which the amount of manganese oxide ranges from 0.10 to solution being represented by the formula 1.0 weight percent calculated as MnO.

References Cited where x, y and z represent a set of m01 ratios and x+y+ z: 1.00, and falling within the polygonal area A-B-C-D- 10 UNITED STATES PATENTS E-F of FIG. 1 of the drawing, the sets of m01 ratios x, y 3 268 453 8/1966 Ouchi et aL 252 62 9 and z of the vertices of said polygonal area being as 33723121 3/1968 E 'n Banno 252-629 f0110WS- 3,424,686 1/1969 ouchi et a1. 252-629 3,463,732 8/1969 Banno et al. 252-629 X y Z 15 A 0.01 0.70 0. 20 TOBIAS E. LEVOW, Primary Examiner B 0.01 0.09 0.90 l C.- 0.05 0.05 0.90 I. COOPER, Assistant Exammer est sa sa F 0110 0170 o20 U.S. Cl. X.R. 

